Theysen

[1.2.2] Realism Overhaul v11.5.1 - 06/12/2017

347 posts in this topic

Posted (edited)

Miscellaneous KSP Questions:

Hi all!  I have gotten back into RO after ver 1.2 was released and have some general questions based on my recent experiences.

  1. Pressure Fed Engines:  Why are pressure fed engines subject to empty ullage issues?  Pressure fed systems use either a bladder tank or a Propellant Management Device to specifically prevent this from occurring.  I can see a certain level of thermal soakback from thrusters causing fuel / ox to vaporize, however inertial effects on fuel should not come into play. 
     
  2. Mechjeb vs. Kerbal Engineer Delta V stats:  I tried eliminating Kerbal Engineer and using Mechjeb for my ship design stats in the VAB.  It gives me different delta v figures when compared to kerbal engineer (usually mechjeb is lower).  Also when a lower stage is added, the delta v numbers for the upper stages change in Mechjeb (not the case for kerbal engineer).  Does anyone know which program is correct? (I'm assuming kerbal engineer is correct)   
     
  3. Astronaut Mass:  Why does the addition of an astronaut into my pod reduces the total delta v in my ship by ~ 1700 dV?  In comparison, the addition of an empty mk1 pod only reduces dV by 600!  Its almost like the astronaut weighs 3 tons!
     
  4. Remote Tech:  
    1. What is the purpose of having a communications satellite network if the DSN stations can communicate up to ~ Jupiter?
    2. Does ksp give the user the proper tools to account for signal delay?  Is there any merit in creating a space station with 5 astronauts (command point)?
Edited by Galile-Ho
1 person likes this

Share this post


Link to post
Share on other sites

@Galile-Ho Hope that i will do a good job answering your questions. So:

  • Being pressure-fed does not mean that ullage is not a problem. This is a common misconception but it is easy to understand why it happens. I will use an excellent example, courtesy of our lord and savior @NathanKell: Pick up a can of spray paint (these containers are pressurized to allow the paint to exit with high velocity from it's nozzle). If you orient it properly (i.e. with the nozzle at the top) then you get the paint. If you place it upside down then you will get just the pressurant. This is exactly what happens in micro-gravity (the "paint" will not cover the outlet, even if the pressure inside the tank is sufficient).
  • MechJeb is usually better at handling stage Dv numbers. KER also has a bug where the Dv numbers do not show up in flight. Personally, i use KER for the per-part management (the info windows are hard to beat here) and maneuver predictions and MJ for all the other goodies.
  • Every crew member has an inert mass of 100 kg. Be aware that there is also a bug where the Kerbal mass is applied to all parts of a craft file so the final values may/will be bogus.
  • Communications are not a problem for deep space but for very low orbits. You can very easily get yourself in a situation where the vessel is between two tracking stations but it cannot reach either of them due to the vessel being over the local horizon. As an example, a correctly positioned GEO relay will allow your vessel to connect with them.
  • The signal delay is part of RemoteTech. RT has a flight computer where you can "program" various actions (action groups, maneuvers, orientation) but is is buggy as hell. I'd advice, even if it utterly unrealistic, to just disable signal delay.
  • You could have a crewed vessel in a low martian orbit and a rover in the surface and let your crew manager it, allowing for near real-time operations. This goes hand in hand with the signal delay feature though so if you disable it then command points are not needed anymore
2 people like this

Share this post


Link to post
Share on other sites

Posted (edited)

Hi everyone, 

I've been playing with RO and RSS for a long time now, and yesterday i decided to make a new fresh install for 1.2.2 with Rp-0, but as a dumb guy i am, i installed all the RO recommended and dependencies + some extra mods, including rp-0, at the same time without testing the game before ... 

So as a result (you may already have seen that coming...), i got a problem in the vab, not all the parts are showing up.. There are only 3 command modules, the VA capsule and a control core and an other one.. 

Before i try to delete one by one each mods, i would like to know if anyone has seen this issue before and if so, what could cause it to happen ? I can't post my gamedata right now but i will if nobody knows this issue..

Thanks a lot to those who will take the time to answer !

Also, huge thanks to the RO team, you guys have my respect for that amazing and intensive work you've done for the ksp community :) 

Edited by Alex38

Share this post


Link to post
Share on other sites
18 hours ago, Galile-Ho said:

Miscellaneous KSP Questions:

Mechjeb vs. Kerbal Engineer Delta V stats:  I tried eliminating Kerbal Engineer and using Mechjeb for my ship design stats in the VAB.  It gives me different delta v figures when compared to kerbal engineer (usually mechjeb is lower).  Also when a lower stage is added, the delta v numbers for the upper stages change in Mechjeb (not the case for kerbal engineer).  Does anyone know which program is correct? (I'm assuming kerbal engineer is correct) 

A workaround for this mechjeb issue is to add an extra decoupler between the troublesome upper stage and the lower stage. 

Share this post


Link to post
Share on other sites

In early career one extra decoupler can make the engineer (the player) bite the desk because of part amount limits... :D

Share this post


Link to post
Share on other sites

@Galile-Ho while @Phineas Freak ably answered your questions (and while I am a mere mortal :P ) I do want to add a bit on the pressure-fed stuff. While it's true that *RCS* and other small maneuvering thrusters generally do use a propellant management system of some sort (and this is simulated by some engines not requiring ullage), most early/mid-period pressure-fed engines *did* require ullage, as I understand it. Certainly this was a concern for Able, which is why it hotstaged. Apollo SPS, also, was only ignited after an RCS burn to settle propellants. Bladder tanks, surface tension devices, and the like, have a mass penalty, and likely the engineers decided not to take that penalty and instead deal with slosh by ullage motors/RCS.

2 people like this

Share this post


Link to post
Share on other sites

@Galile-Ho @NathanKell Per: https://history.nasa.gov/afj/aoh/aoh-v1-2-04-sps.pdf

Apollo didn't always require RCS settling prior to RCS burns, only once about half of the propellent in the tanks was depleted, through some combination of sump tanks and valving. That's probably beyond what Real Fuels will ever support, but it probably worth noting that it's not an all-or-nothing proposition.

However, do you think it would be worth considering having a "Pressurized bladder" tank type whose costs and mass are not that much worse than normal pressurized at low volumes but that gets ruinously massive beyond some "reasonable" size? Then pressure-fed engines could check for either settled fuel in a pressurized tank or any fuel regardless of its stability in a bladder tank.

You could go even further (this is probably getting beyond what's reasonable for gameplay) and have a pump part that would automatically refill bladder tanks from pressurized non-bladder tanks when the fuel is settled at some max rate (to prevent abuse by having a small bladder tank connected to a bigger non-bladder tank).

3 people like this

Share this post


Link to post
Share on other sites

any special folders these mods need to be in, and is Firespitter auto-installed?

Share this post


Link to post
Share on other sites

@Phineas Freak  @NathanKell thanks for your help!

 

  • Can I fix the "bug" that causes me to lose ~ 15% of my total dV due to an astronauts weight?  I'm not clear on how to solve this problem.  
  • I think im generally using mechjeb and KER as you have stated.  KER for ship design, Mechjeb for in-flight stats.  Let me know if im missing something.
  • Will use comm networks to account for earth curvature!  I think I'll play with signal delay until I reach the moon, then its probably getting turned off.
     
  • It seems like the ullage issue is currently being handled by the new engines not requiring ullage.  I'm still pretty low in the tech tree so I can understand how older engines may have been ullage prone.  You could consider simulating the entire feed system (as suggested by @pianojosh), but this does make things more complicated.

    As always, appreciate your efforts in creating/maintaining the game, and still taking time to answer my questions!

Share this post


Link to post
Share on other sites

@Galile-Ho the bug exists only in the editor. It does not occur in flight. So you're safe there. Your best bet is to remove all astronauts in the VAB/SPH during design and instead add 100kg lead ballast tanks surface-attached to the pod as mass simulators. That will give you accurate delta V readouts in the editor. Then at the end remove them and put the astronauts back. Their weights are fine in flight.

 

I tend to prefer to use MJ all the time; KER has some weird staging issues and some issues with RO/RF and the changes it makes, so I prefer MJ, although the part tooltips are very cool.

 

Yeah, were I redoing RF from scratch, I'd make two core changes:

1. No binary distinction between pfed and non, instead each engine would have a required tank pressure and you could set the tank pressure on a scale-bar and that would either work-or-not for pump-fed engines, or cap your chamber pressure for pfed engines.

2. Make ullage tank-side not engine-side, as you folks say.

 

And thanks! :)

1 person likes this

Share this post


Link to post
Share on other sites
16 hours ago, B^2 said:

any special folders these mods need to be in, and is Firespitter auto-installed?

As far as I know all these mods should go in the GameData folder and must maintain their file structure as downloaded. 

If you do not have a Firespitter folder in GameData you must install it separately. 

Share this post


Link to post
Share on other sites
On 09/07/2017 at 2:32 PM, Alex38 said:

Hi everyone, 

I've been playing with RO and RSS for a long time now, and yesterday i decided to make a new fresh install for 1.2.2 with Rp-0, but as a dumb guy i am, i installed all the RO recommended and dependencies + some extra mods, including rp-0, at the same time without testing the game before ... 

So as a result (you may already have seen that coming...), i got a problem in the vab, not all the parts are showing up.. There are only 3 command modules, the VA capsule and a control core and an other one.. 

Before i try to delete one by one each mods, i would like to know if anyone has seen this issue before and if so, what could cause it to happen ? I can't post my gamedata right now but i will if nobody knows this issue..

Thanks a lot to those who will take the time to answer !

Also, huge thanks to the RO team, you guys have my respect for that amazing and intensive work you've done for the ksp community :) 

Hi @Alex38,

Do you use AmpYear ?

I've seen that this mod brokes all command modules in KSP 1.2.2 + RO+RP-0, so I had to uninstall it.

1 person likes this

Share this post


Link to post
Share on other sites
1 hour ago, hargn said:

Hi @Alex38,

Do you use AmpYear ?

I've seen that this mod brokes all command modules in KSP 1.2.2 + RO+RP-0, so I had to uninstall it.

Thanks for the info, yes i installed it!  I'll delete it ! thank you for your help :) 

Share this post


Link to post
Share on other sites

From what I can tell all delta-v maps for realism overhaul say the delta-v required to get from Mars' surface to a circular 200km orbit is 3800m/s, yet I can barely get to a circular 130km orbit with 4500m/s, what am doing wrong?

I'm thinking its to do with my ascent trajectory but I'm not sure how to optimise it

Share this post


Link to post
Share on other sites

Perhaps this question would be better asked in the RO thread?

Share this post


Link to post
Share on other sites

That was the intention I'm new to using forums :/  how do I move this post there?

Share this post


Link to post
Share on other sites
44 minutes ago, Xaovin said:

That was the intention I'm new to using forums :/  how do I move this post there?

You say "beetlejuice" three times, and a moderator moves it for you. :D

1 person likes this

Share this post


Link to post
Share on other sites

thanks!

On 7/11/2017 at 9:24 AM, Nightside said:

As far as I know all these mods should go in the GameData folder and must maintain their file structure as downloaded. 

If you do not have a Firespitter folder in GameData you must install it separately. 

 

Share this post


Link to post
Share on other sites
On 13.7.2017 at 5:53 PM, Xaovin said:

From what I can tell all delta-v maps for realism overhaul say the delta-v required to get from Mars' surface to a circular 200km orbit is 3800m/s, yet I can barely get to a circular 130km orbit with 4500m/s, what am doing wrong?

I'm thinking its to do with my ascent trajectory but I'm not sure how to optimise it

Hi Xaovin, welcome to the forums!

Wild guess: Maybe your TWR is too low or you take too long to go turn your spacecraft. I have flown to orbit from Mars, but cannot recall the delta v I actually needed.

 

Edited by Lilienthal

Share this post


Link to post
Share on other sites
4 hours ago, Lilienthal said:

Hi Xaovin, welcome to the forums!

Wild guess: Maybe your TWR is too low or you take too long to go turn your spacecraft. I have flown to orbit from Mars, but cannot recall the delta v I actually needed.

 

@Xaovin

According to my experience for low TWR (1.20-1.40) it can be around 4800 - 5000 m/s and for very high TWR (more than 2.0)  - 4000 m/s or less but in both cases you need proper ascent profile.

Edited by winged

Share this post


Link to post
Share on other sites

Thanks to linuxgurugamer CKAN now pulls again the right version of Toolbar and should work as intended and usual :):)

Edited by Theysen

Share this post


Link to post
Share on other sites

(deleted)

This problem has been fixed.

Just refresh CKAN and the correct version of the toolbar will be downloaded.

LGG

Edited by linuxgurugamer
1 person likes this

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now